A variety of data entry techniques have been developed to enhance usability and to make computers more versatile. A typical computing environment, especially a computing environment incorporating graphical user interfaces for user interaction, may be optimized for accepting input from one or more discrete input devices. As an example, an individual may enter characters (i.e., text, numerals, and symbols) with a keyboard and control the position of a pointer image on a display with a pointing device, such as a mouse or trackball. A computing environment incorporating graphical user interfaces may also accept input though one or more natural input methods, including speech input methods and handwriting input methods. With regard to speech input methods, the phonemes of the speech input are analyzed to convert the speech input to typewritten text. With handwriting input methods, a pen-like stylus may be utilized to serve the general purpose of a pointing device and create electronic ink, which is analyzed to convert the handwriting into typewritten text.
Another natural input method is touch input, wherein a user touches (e.g., with a finger) a touch-sensitive display to perform actions or activate buttons and menus rendered by the touch-sensitive display. Touch-sensitive displays generally include two components: a display and a touch sensor. The display may be any conventional display, including a cathode ray tube display, an LED display, or a plasma display, for example. Commonly-utilized touch sensors are generally one of a resistive system and a capacitive system. The touch sensor of the resistive system and the capacitive system overlays the display and is at least semi-transparent, thereby permitting the display to be viewed through the touch sensor. Another touch sensor is a surface acoustic wave system. Each of these systems will be described in greater detail below.
The resistive system includes a glass panel that overlays the display. The glass panel is covered with a conductive layer and a resistive layer that are spaced from each other. A scratch-resistant layer may also form an exterior surface of the resistive system. An electric current passes through the conductive layer and the resistive layer while the display is operational. When the user touches and applies pressure to the scratch-resistant layer, the conductive layer and the resistive layer make contact with each other in a corresponding location. A change in the electrical field is noted and coordinates of the point of contact are calculated and translated into input.
The capacitive system includes a capacitive layer that stores electric charge and overlays the display. When the user touches the capacitive layer, a portion of the electric charge is transferred to the user, thereby decreasing the charge on the capacitive layer. The decrease in charge is measured in circuits located at each corner of the capacitive layer, and the computer calculates coordinates of the point of contact from the relative differences in charge at each corner.
The surface acoustic wave system includes two transducers (one receiving transducer and one sending transducer) placed along axes of the display surface. In addition, the surface acoustic wave system includes various reflectors that reflect a signal sent from one transducer to the other transducer. The receiving transducer detects whether a wave has been disturbed by touch and the computer calculates coordinates of the point of contact, which are translated into input.